Highly crystalline TiO₂ nanocuboids have been prepared and their photocatalytic hydrogen generation activity was evaluated via water splitting.

Two-dimensional (2D) hexagonal tin disulfide (SnS ₂ ) nanostructures were prepared via a hydrothermal method using ethylenediamine as a capping agent.

Herein, we synthesized ZnO nanorods using a solvothermal reaction technique at 200 °C for 24 h, and the prepared ZnO nanorods were decorated with silver (Ag) nanoparticles to enhance their photocatalytic activity. The Ag nanoparticles were photochemically deposited on the ZnO rods with varying molar concentrations (from 0.5 to 10 mol%), and their various physicochemical properties were studied. The prepared material was characterised using different spectroscopic techniques. XRD revealed the formation of a highly crystalline hexagonal phase of ZnO. For a higher silver loading (>5 mol%), separate peaks corresponding to cubic silver were observed in the XRD pattern. The photoluminescence spectra of the Ag/ZnO nanostructures show two distinct peaks at 390 and 500 nm; interestingly, the PL intensity of the ZnO emission peak at 500 nm decreases with an increase in the silver concentration. The diffuse reflectance spectra of Ag/ZnO indicate absorbance at 380 nm due to ZnO and a slight hump at 440 nm that corresponds to silver nanoparticles. The FE-SEM and TEM analysis indicates the formation of a hexagonal rod-like morphology, with the lengths of the rods ranging from around 50 to 200 nm and a diameter of around 30 nm. TEM also confirms the presence of Ag nanoparticles with sizes in the range of 20 to 30 nm on the surface of the ZnO nanorods. The photocatalytic activity of the Ag/ZnO nanostructures was evaluated by following the degradation of methylene blue (MB) dye under a 400 W mercury vapour lamp. ZnO with 10 mol% Ag loading shows the highest photocatalytic activity as compared to the 0.5, 1 & 5 mol% Ag–ZnO catalysts. The observed apparent rate constant for the photocatalytic MB degradation using 10 mol% Ag–ZnO (K_app = 6.01 × 10⁻² min⁻¹) was six times that of pure ZnO (K_app = 1.09 × 10⁻² min⁻¹). A gradual increase in the photocatalytic activity of Ag/ZnO was observed with an increase in the silver concentration. The photocurrent response of the prepared Ag–ZnO nanostructures was examined by a photoconductivity study. Moreover, the photocatalytic performance of the sample was correlated with the photoconductivity of the samples. The photoconductivity of the samples was stable, and the photoconductivity of 10 mol% Ag–ZnO was almost 20 times that of pure ZnO, resulting in a higher photocatalytic activity.

Schematic of photocatalytic H₂ generation using Ni/SnS₂ nanosheets along with the energy levels of SnS₂ and Ni nanostructures.

One-dimensional ZnO nanostructures were synthesized using solvothermal reaction method, and in situ CdS nanoparticles were grown on 1D ZnO having different CdS compositions such as 0.1, 0.5, 1 and 5 mol% using microwave reaction system. The prepared CdS/ZnO coupled semiconductor catalysts were characterized using various spectroscopic techniques. XRD analysis indicated the presence of a wurtzite structure for all the prepared CdS/ZnO compositions. DRS spectrum showed red shift in the absorbance edge of CdS/ZnO nanocomposites with increasing CdS mol% and absorbance increases in 400 to 500 nm range. Photoluminescence spectra illustrated two emission peaks, with the first one at 390 nm due to the band edge emission of ZnO and the second broad peak centered around 480 nm possibly due to CdS band edge emission or oxygen vacancies in ZnO. FESEM image showed the formation of pencil shaped one-dimensional ZnO nanorods containing spherical CdS nanoparticles on the surface of ZnO. TEM analysis confirms the rod-like morphology of ZnO and the presence of CdS nanoparticles. The activity of the prepared CdS/ZnO catalysts was evaluated by measuring the amount of H₂ generated during photocatalytic H₂ evolution from water. The photocatalytic activity of prepared coupled CdS/ZnO shows an increase in hydrogen generation compared to that of individual ones. CdS loading enhances the rate of H₂ generation and is the highest for 5 mol% CdS/ZnO composition.